Masahito Morita

Microglial transplantation increases amyloid-β clearance in Alzheimer model rats

Immunization with amyloid‐β (Aβ) peptides, a therapeutic approach in Alzheimers disease (AD), reduces brain Aβ, and microglial Aβ phagocytosis has been proposed as an Aβ‐lowering mechanism. We transplanted rat microglia into the rat lateral ventricle just after intra‐hippocampal Aβ injection, and then investigated the contribution of exogenous microglia to Aβ clearance. Migration of exogenous microglia from the lateral ventricle to Aβ plaque was detected by magnetic resonance imaging and histochemical analysis, and the clearance of Aβ was increased by transplantation. These results suggest the possible usefulness of exogenous microglia to the therapeutic approach in AD.

DJ-1 protects against neurodegeneration caused by focal cerebral ischemia and reperfusion in rats

Reactive oxygen species (ROS) is massively produced in the brain after cerebral ischemia and reperfusion. It reacts strongly with cellular components, which has detrimental effects and leads to neuronal cell death. DJ-1, which was found to be the causative gene of familial Parkinsons disease PARK7, is a multifunction protein, which plays a key role in transcriptional regulation, and a molecular chaperone. In this study, we investigated the neuroprotective effect of DJ-1 against neurodegeneration caused by ischemia/reperfusion injury. Cerebral ischemia was induced in rats by 120 mins of middle cerebral artery occlusion (MCAO) using an intraluminal introduction method. The intrastriatal injection of recombinant glutathione S-transferase-tagged human DJ-1 (GST-DJ-1) markedly reduced infarct size in 2,3,5-triphenyltetrazolium chloride staining at 3 days after MCAO. In addition, we performed a noninvasive evaluation of ischemic size using magnetic resonance imaging and found a significant reduction of infarct size with the administration of GST-DJ-1. In GST-DJ-1-treated rats, behavioral dysfunction and nitrotyrosine formation were significantly inhibited. Furthermore, GST-DJ-1 markedly inhibited H2O2-mediated ROS production in SH-SY5Y cells. These results indicate that GST-DJ-1 exerts a neuroprotective effect by reducing ROS-mediated neuronal injury, suggesting that DJ-1 may be a useful therapeutic target for ischemic neurodegeneration.

Preparation for highly sensitive MRI contrast agents using core/shell type nanoparticles consisting of multiple SPIO cores with thin silica coating.

We describe here the facile and robust preparation methods for the multiple-SPIO-containing silica-coated core/shell type nanoparticles which can serve as a highly sensitive MRI contrast agent. The imidazolium-tethered core/shell type particles were synthesized, and the centrifugal selection for the multiple-SPIO-containing particles and the etching process to fabricate thin silica layers were carried out to improve the proton relaxivity of water tissue. We found that the synthetic particles can provide approximately 7-fold clearer contrasts than that of the particles before treatments. In addition, the particles can show good dispersibility at least for 1 week in aqueous media.

Simple PEG conjugation of SPIO via an Au-S bond improves its tumor targeting potency as a novel MR tumor imaging agent.

Gold/iron oxide magnetic nanoparticles are hybrid nanoparticles containing a core of magnetic iron oxide and surface colloidal gold, which allows for various biomaterials to be immobilized on the surface of the iron oxide nanoparticles via colloidal gold. Here, we developed a novel magnetic resonance (MR) imaging agent to broaden the MR tumor-imaging spectrum of superparamagnetic iron oxide nanoparticles (SPIO), e.g., Feridex(), a clinical MR imaging agent for diagnosing liver cancer. Au/Feridex was synthesized by electron beam irradiation, and thiol-modified poly(ethylene glycol) (PEG-SH) was easily conjugated to its surface via an Au-S bond without the need for any chemical reactions. PEG conjugation of Au/Feridex enhanced its accumulation in Meth-A tumor tissue and decreased its accumulation in normal liver tissue. In addition, MRI using PEG-Au/Feridex, in contrast to MRI using unmodified Au/Feridex and Feridex, detected B16BL6 and Meth-A tumor tissues in vivo. This finding indicates that PEG-Au/Feridex is useful for diagnosing various types of tumors. In addition, because the synthesis of PEG-Au/Feridex is simple and high yields are easily produced, PEG-modified SPIO for tumor diagnosis can be prepared on an industrial scale with low cost.

Assembly system of direct modified superparamagnetic iron oxide nanoparticles for target-specific MRI contrast agents.

We report the direct modification of SPIOs with a biomolecule and the target-specific assembly system of these modified SPIOs for using MRI contrast agents. The transverse relaxation rate of the aqueous solutions containing the modified SPIOs was altered by the dispersion state.

Magnetic resonance imaging using hemagglutinating virus of Japan-envelope vector successfully detects localization of intra-cardially administered microglia in normal mouse brain

Although the therapeutic use of microglia has received some attention for the treatment of brain diseases, few non-invasive techniques exist for monitoring the cells after administration. Here, we present a technique using magnetic resonance imaging (MRI) to track microglia injected intra-cardially. We labeled microglia expressing enhanced green fluorescent protein with superparamagnetic iron oxide (Resovist) using the hemagglutinating virus of Japan-envelope vector. We injected labeled microglia into the left ventricle of the heart of mice. After monitoring exogenously administered microglia in the mouse brain in vivo using T(2)*-weighted MRI at a magnetic field of 7T, we compared the MR images with histochemical localization of exogenous microglia in vitro. MRI revealed clear signal changes attributable to Resovist-containing microglia in the mouse brain. Histochemistry demonstrated the presence of exogenous microglia in the brain at the same locations shown by MRI. This study demonstrates the usefulness of MRI for non-invasive monitoring of exogenous microglia, and suggests a promising future for microglia/macrophages as therapeutic tools for brain disease.

MR tracking of transplanted glial cells using poly-l-lysine-CF3

Magnetic resonance (MR) imaging using super-paramagnetic iron oxides (SPIOs) is a powerful tool to monitor transplanted cells in living animals. Since, however, SPIOs are negative contrast agents, positive agents have been explored. In this study, we examined the feasibility of FITC-labeled poly-L-lysine-CF3 (PLK-CF3) using glial cells. FITC-labeled PLK-CF3 was easily internalized by neuroblastoma cells and glia as adding it into culture medium. No toxicity was seen at the concentration of less than 80 microg/ml. MR images positively detected labeled cells transplanted in the brain of living mouse. The results indicate that FITC-labeled PLK-CF3 is a useful positive contrast agent for MR tracking.

Glycothermal Synthesis and Magnetic Properties of YIG/YAG Nanoparticles

Yttrium aluminum garnet (YAG) nanoparticles of 14.5±3.2 nm in diameter are synthesized from yttrium acetate and aluminum isopropoxide in 1,4-butanediol by autoclave treatment at 300oC for 2h. Yttrium iron garnet (YIG) / YAG composite nanoparticles of 21.1±4.9 nm in diameter are synthesized from yttrium acetate and iron(III) acetylacetonate in 1,4-butanediol by autoclave treatment at 300oC for 2h using YAG nanoparticles as the seed. In contrast, YIG is not formed by the same procedure in the absence of the YAG seed. The saturation magnetizations of nanoparticles with different YIG/YAG ratios range from 11.9 to 17.8 emu/g. YIG/YAG nanoparticles dispersed in the agarose gel are observed by magnetic resonance imaging (MRI). The degree of the negative MRI contrast depends on the concentration of YIG/YAG nanoparticles.

Fluorescent and Magnetic Resonance Imaging by Rare Earth Doped Nanoparticles with Garnet Structure

Yb 3+ doped Y 3 Al 5 O 12 (YAG:Yb 3+ ) nanoparticles are prepared from yttrium acetate tetrahydrate, ytterbium acetate tetrahydrate and aluminum isopropoxide in 1,4-butanediol by autoclave treatment at 300 °C for 2 h. Moreover, Gd-YAG:Yb 3+ nanoparticles are prepared from the mixture of YAG:Yb 3+ colloidal solution and gadolinium acetate tetrahydrate by the same autoclave treatment as YAG:Yb 3+ . Properties of structure, near infrared photoluminescence and magnetic resonance contrast enhancement are characterized for as-prepared and calcined YAG:Yb 3+ and Gd-YAG:Yb 3+ nanoparticles.